I am begining to refurbish an old Farmall Cub and am planning to use the electrolysis rust removal process on the smaller parts - battery case, tool box, light housing, etc.  Does the paint need to be removed prior to electrolysis, or can I chemically remove any remaining paint after the rust  attack?  Thanks

Electrolysis works best on small parts.  Or rather the size doesn't matter as much as the weight.
The heavier the mass of metal you are working, the more power it takes.
In other words, you can do a cookie sheet quick and easy.  But a 10 pound wrench takes a much longer time at the usual 6 amps.   (cheap battery charger)

  Paint (or plating) will stay put fine during electrolysis. Provided the metal underneath is sound and clean. If the metal has rust under the surface finish, whatever is on there, it will boil right off.
  If it has rust underneath it is already unstable and won't stay anyway.

I think they use heavy DC arc welders and swimming pools to de-rust pirate ship cannons.

But tractor parts are a --lot-- faster sand blasting. This is the standard method for these. Preserving the original surface is not important on tractors.
Try a small pressure sand blaster. You want the kind with a cap that screws on tight.
The open drum kind of blaster, well you must have a huge air compressor to really utilize those.  But the small pressure blasters can give good service once you get used to them.
      yours Scott
 

http://z6.invisionfree.com/ToolBoxTalk/index.php?showtopic=206

http://z6.invisionfree.com/ToolBoxTalk/index.php?showtopic=1581
No point to me typing what the master has already said.

Even after you sand blast and prime you can still get rust bleed through.  We use a product called Rust Ender. www.theshopproducts.com/products.  We've build from bare metal 3 tractors and we're working on a 1010 Deere, a '46 UTU Moline and a '36 Twin Cities.  Follow the directions and the black coat kills the rust and makes a fine primer coat for the finish coat.  Or you can leave the ender coat on as a final coat outside and no rust, if you don't mind the black color.

As a former Battery repairman, the axiom 'Sulphuric acid never sleeps' was a fact that we had to live with. Once a steel cell tray on a forklift battery begins to rust, you could not stop it by sanding, blasting or neutralization. You can only slow it down. From the description in Aunt Phil's post, it sounds like electrolysis MIGHT be a good way to prep the battery box. I have not tried it, but it sounds like it will remove the Ferric Sulfate from the grain boundaries of the steel.

THIS DAMN BOARD IS NOW TIMING OUT REPLYS AT 12 SECONDS!!!

Hmmm, battery repair, as in chop pitch out and replace posts and cell connectors?  If so, what dark secrets have you that I need to know?  I haven't been able to find a repairman since 75.

OK, tractor battery box = multi step process or wasted effort.

1, soak box in clear water, heat optional to leach sulphuric deposits & salts.
repeat till water is clear.  If box can't be submerged load with wet NEW catlitter and heat gently, no hotter than 200°.

2, After soak returns clear, I'd chelate the box in molasses.  Chelation will remove oxygen from any salts left in the metal without damaging the metal.

Unfortunately you will probably have holes where the box is already rotted. 

3, when clean drown the inside of the box with asphaltic roof coating diluted with mineral spirits, preferably allowing soak time.  Let asphaltic coating dry slowly.

4, topcoat with Rustoleum

The electroplating process would NOT be my first choice due to potential tank contamination by the acid salts.  It takes damn little acid to ruin a tank charge as I've learned from rainwater.

Base neutralizing acid salts in steel is damn near impossible, doing so requires heat, time and strong caustics, such as the old hottanks engines were cooked in before EPA.

There are a couple other tricks, but I ain't at liberty to divulge them.  You know where the Guru lives, and if he wants to tell you he will.

>Base neutralizing acid salts in steel is damn near impossible

It's not just the acidity, sulphur is a particular problem with mild steel, sulphur unusually is soluable in steel, something the folks making railroad track learned the hard way a century or so ago. Once the sulphur has migrated deep into the steel, there isn't any way to get it out short of melting the steel down. And once it's in there, it combines with certain alloy metals and splits the grain. The only thing left is to keep it dry......

I have just finished my first attempt using electrolysis. It worked very well removing the rust and was very easy. My only problem is that it turned one of the items very black.

The items #1 1930-40 tack puller will be my first Perfect Handle project. I will use fresh maple that I am in the process of drying.

#2 six inch section of RR track that I will make a small bench top anvil from.

Electrolysis turned both items black. This is not a problem with the puller as it was black to begin with. But the track section turned pitch black and so far a wire wheel doesn't phase it. Well maybe a black anvil isn't sooo bad but I really would like it to shine. Suggestions would be greatly appreciated.

I will say tho that there is not a speck of rust anywhere. I quickly washed both Items, dried, and oiled them heavily. I will have to wait until my maple is ready to complete the handle for the tack puller. I will try to get some pics up.  Oh since I really don't have a place to store my electrolyte container the lawn got a good dose of high iron fertilizer.

Well I did try pics.  I will put them on photobucket and see if it works.

http://s1140.photobucket.com/albums/n563/ietech/Perfect%20Handle%20Project/?albumview=slideshow

Gee, I wonder where you got the maple...

Actually, the track looks good in black to me.  My track section started out black, and I like it.

LOL Yeah That huge tree in my back yard.  You know the one.

I'm trying to speed up the drying but my piece is already beginning to crack. I soaked it in water for a few days when the cracking started then removed it and placed in front of my garage heater. I will keep it there for a couple of days and see if the cracking slows down. Maybe next it's to the microwave but I think SWMBO will frown on that. LOL

I did get the pics on photobucket in the last post.

Soaking in water used to be the way to prevent checking in timbers.  One of the founding fathers -- Hamilton, I think -- received as a wedding present from his wife's father,  a lot of timber for building his house.  It was specified as being sunk in a pond for seasoning.

The trick is that it must be submerged for a significant period of time.  Timber bamboo takes at least a month under water.  The old beams were sunk for 6 months or a year.

Yard sale microwaves can be had cheap. 

I'm thinking that maple you gave me will do very well for a new handle for the PH screwdriver John K gifted me.

Quote from: Ietech on January 22, 2012, 05:04:25 PM
I have just finished my first attempt using electrolysis. It worked very well removing the rust and was very easy. My only problem is that it turned one of the items very black.

The items #1 1930-40 tack puller will be my first Perfect Handle project. I will use fresh maple that I am in the process of drying.

#2 six inch section of RR track that I will make a small bench top anvil from.

Electrolysis turned both items black. This is not a problem with the puller as it was black to begin with. But the track section turned pitch black and so far a wire wheel doesn't phase it. Well maybe a black anvil isn't sooo bad but I really would like it to shine. Suggestions would be greatly appreciated.

I will say tho that there is not a speck of rust anywhere. I quickly washed both Items, dried, and oiled them heavily. I will have to wait until my maple is ready to complete the handle for the tack puller. I will try to get some pics up.  Oh since I really don't have a place to store my electrolyte container the lawn got a good dose of high iron fertilizer.

Well I did try pics.  I will put them on photobucket and see if it works.

http://s1140.photobucket.com/albums/n563/ietech/Perfect%20Handle%20Project/?albumview=slideshow

With the electro process you either wash the black off as soon as it comes out of the tank or you get to liking black.   If it drys it stays!
Dawn dishwashing soap seems to work best in the washing process.

Thanks for the washing idea I guess I'll have to learn to like the black. I think it's too late but I'll try it anyway. I did wash it but no soap --- Oh well I'll know better next time. Thx

Rich

One thing you can TRY, and bear in mind there is no guarantee it will work.

Throw the objects into a bucket of soda water and let them soak for a day.  Then put the juice to them again for a few hours.  The BLACK crud may soften and loosen up so you can wash it away.  You won't hurt good metal that's there by recooking.  If it doesn't work you rally haven't lost a lot.

My experience is that Black crud is in great degree a function of the water used in the tank.  In some areas the tap water is damn acidic and causes the tank to perform poorly.  I had to reload a tank some years back because it got flooded by rainwater & went acidic.  You might want to check yours with one of the cheap PH meters used for gardening.

Beyond that I'm not too sure I can be of help.  The tanks I play with have gone a way beyond a battery charger & bucket.  We use carbon collecting electrodes and run constant filtration which results in a crystal clear electrolyte.  We also electrodecontaminate after pressure washing before anything goes in the derusting tank.